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.TH POSIX_FALLOCATE 3C "Jul 14, 2008"
.SH NAME
posix_fallocate \- file space control
.SH SYNOPSIS
.LP
.nf
#include <fcntl.h>

\fBint\fR \fBposix_fallocate\fR(\fBint\fR \fIfd\fR, \fBoff_t\fR \fIoffset\fR, \fBoff_t\fR \fIlen\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBposix_fallocate()\fR function ensures that any required storage for
regular file data starting at \fIoffset\fR and continuing for \fIlen\fR bytes
is allocated on the file system storage media. If \fBposix_fallocate()\fR
returns successfully, subsequent writes to the specified file data will not
fail due to the lack of free space on the file system storage media.
.sp
.LP
If the \fIoffset\fR+\fIlen\fR is beyond the current file size, then
\fBposix_fallocate()\fR adjusts the file size to \fIoffset\fR+\fIlen\fR.
Otherwise, the file size is not changed.
.sp
.LP
Space allocated with \fBposix_fallocate()\fR is freed by a successful call to
\fBcreat\fR(2) or \fBopen\fR(2) that truncates the size of the file. Space
allocated with \fBposix_fallocate()\fR may be freed by a successful call to
\fBftruncate\fR(3C) that reduces the file size to a size smaller than
\fIoffset\fR+\fIlen\fR.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBposix_fallocate()\fR returns zero. Otherwise, an
error number is returned to indicate the error.
.SH ERRORS
.sp
.LP
The \fBposix_fallocate()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The \fIfd\fR argument is not a valid file descriptor or references a file that
was opened without write permission.
.RE

.sp
.ne 2
.na
\fB\fBEFBIG\fR\fR
.ad
.RS 10n
The value of \fIoffset\fR+\fIlen\fR is greater than the maximum file size.
.RE

.sp
.ne 2
.na
\fB\fBEINTR\fR\fR
.ad
.RS 10n
A signal was caught during execution.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIlen\fR argument is less than or equal to zero, or the \fIoffset\fR
argument is less than zero, or the underlying file system does not support this
operation.
.RE

.sp
.ne 2
.na
\fB\fBEIO\fR\fR
.ad
.RS 10n
An I/O error occurred while reading from or writing to a file system.
.RE

.sp
.ne 2
.na
\fB\fBENODEV\fR\fR
.ad
.RS 10n
The \fIfd\fR argument does not refer to a regular file.
.RE

.sp
.ne 2
.na
\fB\fBENOSPC\fR\fR
.ad
.RS 10n
There is insufficient free space remaining on the file system storage media.
.RE

.sp
.ne 2
.na
\fB\fBESPIPE\fR\fR
.ad
.RS 10n
The \fIfd\fR argument is associated with a pipe or FIFO.
.RE

.SH USAGE
.sp
.LP
The \fBposix_fallocate()\fR function has a transitional interface for 64-bit
file offsets. See \fBlf64\fR(7).
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See \fBstandards\fR(7).
.TE

.SH SEE ALSO
.sp
.LP
.BR creat (2),
.BR open (2),
.BR unlink (2),
.BR ftruncate (3C),
.BR attributes (7),
.BR standards (7)
